package com.tz.test.util;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Date;
import java.util.List;
import java.util.concurrent.*;

/**
 * @author zhangky
 * @since 2020/4/24
 *
 * 继承ThreadPoolExecutor类，覆盖了shutdown(), shutdownNow(), beforeExecute() 和 afterExecute()
 * 方法来统计线程池的执行情况
 * <p>
 * Created by on 2019/4/19.
 */
public class ThreadPoolMonitor extends ThreadPoolExecutor {

    private static final Logger LOGGER = LoggerFactory.getLogger(ThreadPoolMonitor.class);

    /**
     * 保存任务开始执行的时间，当任务结束时，用任务结束时间减去开始时间计算任务执行时间
     */
    private ConcurrentHashMap<String, Date> startTimes;

    /**
     * 线程池名称，一般以业务名称命名，方便区分
     */
    private String poolName;

    /**
     * 调用父类的构造方法，并初始化HashMap和线程池名称
     *
     * @param corePoolSize    线程池核心线程数
     * @param maximumPoolSize 线程池最大线程数
     * @param keepAliveTime   线程的最大空闲时间
     * @param unit            空闲时间的单位
     * @param workQueue       保存被提交任务的队列
     * @param poolName        线程池名称
     */
    public ThreadPoolMonitor(int corePoolSize, int maximumPoolSize, long keepAliveTime,
                             TimeUnit unit, BlockingQueue<Runnable> workQueue, String poolName) {
        this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
                Executors.defaultThreadFactory(), poolName);
    }

    /**
     * 调用父类的构造方法，并初始化HashMap和线程池名称
     *
     * @param corePoolSize    线程池核心线程数
     * @param maximumPoolSize 线程池最大线程数
     * @param keepAliveTime   线程的最大空闲时间
     * @param unit            空闲时间的单位
     * @param workQueue       保存被提交任务的队列
     * @param threadFactory   线程工厂
     * @param poolName        线程池名称
     */
    public ThreadPoolMonitor(int corePoolSize, int maximumPoolSize, long keepAliveTime,
                             TimeUnit unit, BlockingQueue<Runnable> workQueue,
                             ThreadFactory threadFactory, String poolName) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory);
        this.startTimes = new ConcurrentHashMap<>();
        this.poolName = poolName;
    }

    /**
     * 线程池延迟关闭时（等待线程池里的任务都执行完毕），统计线程池情况
     */
    @Override
    public void shutdown() {
        // 统计已执行任务、正在执行任务、未执行任务数量
        LOGGER.info("{} Going to shutdown. Executed tasks: {}, Running tasks: {}, Pending tasks: {}",
                this.poolName, this.getCompletedTaskCount(), this.getActiveCount(), this.getQueue().size());
        super.shutdown();
    }

    /**
     * 线程池立即关闭时，统计线程池情况
     */
    @Override
    public List<Runnable> shutdownNow() {
        // 统计已执行任务、正在执行任务、未执行任务数量
        LOGGER.info("{} Going to immediately shutdown. Executed tasks: {}, Running tasks: {}, Pending tasks: {}",
                this.poolName, this.getCompletedTaskCount(), this.getActiveCount(), this.getQueue().size());
        return super.shutdownNow();
    }

    /**
     * 任务执行之前，记录任务开始时间
     */
    @Override
    protected void beforeExecute(Thread t, Runnable r) {
        startTimes.put(String.valueOf(r.hashCode()), new Date());
    }

    /**
     * 任务执行之后，计算任务结束时间
     */
    @Override
    protected void afterExecute(Runnable r, Throwable t) {
        Date startDate = startTimes.remove(String.valueOf(r.hashCode()));
        Date finishDate = new Date();
        long diff = finishDate.getTime() - startDate.getTime();
        // 统计任务耗时、初始线程数、核心线程数、正在执行的任务数量、
        // 已完成任务数量、任务总数、队列里缓存的任务数量、池中存在的最大线程数、
        // 最大允许的线程数、线程空闲时间、线程池是否关闭、线程池是否终止
        LOGGER.info("{}-pool-monitor: " +
                        "Duration: {} ms, PoolSize: {}, CorePoolSize: {}, Active: {}, " +
                        "Completed: {}, Task: {}, Queue: {}, LargestPoolSize: {}, " +
                        "MaximumPoolSize: {},  KeepAliveTime: {}, isShutdown: {}, isTerminated: {}",
                this.poolName,
                diff, this.getPoolSize(), this.getCorePoolSize(), this.getActiveCount(),
                this.getCompletedTaskCount(), this.getTaskCount(), this.getQueue().size(), this.getLargestPoolSize(),
                this.getMaximumPoolSize(), this.getKeepAliveTime(TimeUnit.MILLISECONDS), this.isShutdown(), this.isTerminated());
    }

    /**
     * 创建固定线程池，代码源于Executors.newFixedThreadPool方法，这里增加了poolName
     *
     * @param nThreads 线程数量
     * @param poolName 线程池名称
     * @return ExecutorService对象
     */
    public static ExecutorService newFixedThreadPool(int nThreads, String poolName) {
        return new ThreadPoolMonitor(nThreads, nThreads, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<>(), poolName);
    }

    /**
     * 创建缓存型线程池，代码源于Executors.newCachedThreadPool方法，这里增加了poolName
     *
     * @param poolName 线程池名称
     * @return ExecutorService对象
     */
    public static ExecutorService newCachedThreadPool(String poolName) {
        return new ThreadPoolMonitor(0, Integer.MAX_VALUE, 60L, TimeUnit.SECONDS, new SynchronousQueue<>(), poolName);
    }
}